(5 Mr. Donovan 07i Galvanometric Deflections 



of the same metal, are rubbed against each other, deflection will result, the 

 degree of which will vary with tlie metals or metal employed, and to a certain 

 extent with the force and rapidity of attrition. This deflection will take place 

 in air, or under the surface of mercury, or of aqueous, oily, ethereal, or alcoholic 



liquids. 



Law III. When two diff'erent metals, and sometimes two separated m-asses 

 of the same metal, are brought in contact, at unequal temperatures, deflection 

 will generally take place, the degree being determined by the nature of the 

 metals or metal, and the difference of the temperatures at which the contact is 



effected. 



Law IV. If two different metals be at the same temperature through- 

 out their mass, whether it be high, low, or mean, contact will not produce 

 deflection. 



Law V. 1. Sometimes the deflective energy developed by attrition, at 

 unequal temperatures, is more effective than that produced by contact, when 

 the temperatures are in a state of inequality to the same amount as that at 

 which attrition took place. 



2. And sometimes the deflective energy of two metals in contact, at unequal 

 temperatures, is more effective than that developed by their attrition when their 

 temperatures are in a state of inequality to the same amount. The result 2 

 is of less frequent occurrence than 1. 



Law VI. When two metals, at luiequal temperatures, produce deflection 

 on the same side of the magnetic meridian, both by their attrition and contact ; 

 while if their temperatures be equal, their attrition causes deflection on the 

 opposite side of the magnetic meridian ; it is a consequence that the deflection 

 caused by attrition or contact of the metals, while their temperature is ade- 

 quately unequal, will change to the opposite side of the magnetic meridian if 

 attrition be employed during the period of their near approach to and arrival 

 at equality of temperature. 



Law VII. If the deflections be all on the same side of the magnetic meri- 

 dian which are produced, first, by the contact or attrition of two metals at 

 unequal temperatures, and, second, by their attrition at equal temperatures ; 

 then it is but another mode of expression to say that there can be no such 

 reversal as in Law vi. 



